Air entrainment compositions for cement compositions

ABSTRACT

Compositions and methods relating to cementitious compositions are provided. The use of a blend of a rosin and a tannin to entrain air into cementitious compositions is provided. A blend of a rosin and a tannin in a weight ratio of 10:1 to 1:10 are added to a wet cementitious composition at levels of less than 1% by weight based on the weight of the cement and air is mixed into the cement. The resulting cement will contain, e.g. 5% to 10% by volume air which improves the resistance of the set cement to freeze damage. Also provided is a method of entraining air into a cementitious composition which employs such a blend.

FIELD OF THE INVENTION

This invention relates to naturally derived compositions useful forentraining air in cement compositions.

BACKGROUND ART

It is usual practice to add air entraining agents to cement based mixessuch as concrete and mortar, in order to entrain microscopic bubbles ofair in the mixture. This imparts certain advantages to the concrete ormortar. It plasticizes the mix, making it more workable, and in thisrespect the entraining agent often acts as a replacement, at least inpart, for lime. When the concrete or mortar sets the entrained bubblesincrease its elasticity, its resistance to salt solutions and,particularly, its resistance to frost damage.

Air entraining agents are generally surfactant mixtures which produce afoam in the cement that persists so that the set cement contains manysmall, generally spherical, air voids, e.g. that measure from 10micrometers to 250 micrometers in diameter. These air voids are thoughtto alleviate internal stresses in the cement that are caused whenmoisture freezes in the pores in the cement that are inherently formedduring setting of the cement. In practice, up to about 10% air by volumeof the cement is entrained into the cement to be placed in severeenvironments.

SUMMARY OF THE INVENTION

This invention relates generally to a blend composition that is usefulfor entraining air into cementitious compositions. In one aspect, thisinvention relates to composition useful for entraining air into acementitious composition comprised of a blend consisting essentially ofa rosin and a tannin in a ratio by weight of from about 10:1 to about1:10. In certain embodiments, said composition is an essentially drypowder, e.g. it has a moisture content of less than about 20% by weightand preferably a sufficiently low moisture content to render said drypowder flowable. In preferred embodiments, the blend further contains analkaline material in an amount sufficient to neutralize said blend, i.e.impart to an aqueous dispersion or solution of said blend an essentiallyneutral or alkaline pH, e.g. a pH of from about 6 to about 13.

In a related aspect, this invention relates to an aqueous dispersion orsolution comprised of a minor amount by weight of a blend consistingessentially of a rosin and a tannin in a ratio by weight of from about10:1 to about 1:10, and a major amount by weight of water. The aqueousdispersion or solution will typically contain said blend at a solidscontent of from about 5% to about 50% by weight, more typically fromabout 10% to about 15%. In preferred embodiments, said aqueousdispersion or solution further contains an alkaline material in anamount sufficient to neutralize said blend, i.e. impart to an aqueousdispersion or solution of said blend an essentially neutral or alkalinepH, e.g. a pH of from about 6 to about 13. Both the aqueous compositionand flowable powder are useful as additives in industrial products suchas hydraulic cement mixes.

In another aspect, this invention relates to a cementitious compositioncomprising a hydratable cementitious material in a major amount byweight and an air entrainment agent consisting essentially of a rosin ina minor amount by weight of said cementitious composition and a tanninand in a minor amount by weight of said cementitious composition, theratio by weight of said rosin to said tannin ranging from about 10:1 toabout 1:10. In preferred compositions, from about 0.0005% to about 0.5%by weight (dry basis) of a blend of a rosin and a tannin based on weightof cement is present to entrain air into the cementitious composition.

In a related aspect, this invention relates to a method of entrainingair into a cementitious composition comprising mixing a minor amount byweight of an air entrainment agent consisting essentially of a rosin anda tannin in a ratio by weight of from about 10:1 to about 1:10 withmajor amount by weight of a hydratable cementitious compositioncomprised of a cement and water, the amount of said air entrainmentagent being effective to entrain from about 1% to about 20% by volume ofair into said cementitious composition.

DETAILED DESCRIPTION OF THE INVENTION

Rosin is predominantly comprised of a complex mixture of monocarboxylicacids of alkylated hydrophenanthrene compounds which are isolated frompine trees. The monocarboxylic acids represent about 90% by weight ofmost commercially available rosins. Gum rosin is sometimes also known ascolophony and is derived from various species of pine trees, which whentapped yield an oleoresinous product known as crude turpentine. Steamdistillation removes the oil of turpentine and leaves the solid rosin.Ranging in color from pale yellow to dark brown, gum rosin is usuallysoft, brittle and practically transparent. It has an aromatic odor andis soluble in alcohol, acetic acid and volatile and mixed oils.Typically, the specific gravity ranges from 1.045 to 1.085. Thesoftening point is about 75° C. or 167° F. with a melting point of about120° to 135° C. With regard to its chemistry, gum rosin consists almostentirely of abietic acid possibly in the form of isomers thereof.

In addition to the historic gum rosin, there are two other types ofrosin products commercially available, wood rosin and tall oil rosin.Wood rosin is a rosin product isolated from aged pine stumps left fromeither the clearing of land for farming or lumbering operations. Thestumps are shredded and the resulting wood chips are soaked in anorganic solvent under elevated temperature and pressure. The extract isdistilled to collect nonvolatile crude rosin, volatile extractibles andrecovered solvent. Tall oil rosin is a by-product of pulping. Raw woodchips are digested under heat and pressure with caustic and sodiumsulfide. Soluble sodium salts of lignin, rosin and fatty acids are in asolution separated from the wood pulp. The fatty acids and rosin floatto the top of the solution and are skimmed off and acidified to free therosin and fatty acids. This mixture is known as crude tall oil and isrefined by fractional distillation to produce tall oil rosin and talloil fatty acids.

The characteristics and properties of rosins are well known in the art.Rosins, their properties, manufactures, and uses are described, forexample, in "Resins, Natural", Encyclopedia of Polymer Science andEngineering, vol. 14, pp. 438-444 (John Wiley & Sons, Inc. N.Y., N.Y.,1988), the disclosure of which is incorporated herein by reference.

Tannins are plant-derived polyhydroxyphenolic compounds characterized bytheir ability to precipitate proteins. The tannin component can beobtained from the various wood and vegetation materials found throughoutthe world. Tannins are a large group of water-soluble, complex organiccompounds. Almost every tree or shrub that grows contains some tanninsin the leaves, twigs, barks, wood or fruit. Examples of barks arewattle, mangrove, oak, eucalyptus, hemlock, pine, larch and willow.Examples of woods are the quebracho, chestnut, oak and urunday. Examplesof fruits are myrobalans, valonia, divi-divi, tara, and algarobilla.Examples of leaves are sumac and gambier and examples of roots arecanaigre and palmetto. Specific examples of plants which may be used asa source of tannin (with the principal country or region of availabilitybeing shown in parentheses) include: wattle, also known as acacia ormimosa (South Africa, South America, especially Brazil); quebracho(Argentina, Paraguay and Brazil); chestnut (France and Italy);myrabolans (India); mangrove (swampy, tropical areas such as southernFlorida, Columbia, Brazil, Africa); divi divi (western coast of SouthAmerica); tara (Peru); sumac (Sicily, Albania and Yugoslavia); cypress(United States); gambler (Malaysia, Sumatra, Borneo); and chestnut oak(blighted in the United States, but available from numerous othersources).

The tannins can be categorized into the traditional "hydrolyzable"tannins and "condensed" tannins. Examples of condensed tannin extractsare those manufactured from the bark of the black wattle tree (or mimosatannin of commerce), from the wood of the quebracho tree (Spanish:Quebra hacha, axe-breaker,) from the bark of the hemlock tree, and fromthe bark of several commonly used pine species. The preparation ofwattle and quebracho extracts is a well established industrial practiceand such extracts are freely available in considerable amounts.Preferred tannins are in their native form as extracted and have notbeen chemically modified, e.g. by oxidation or by alkaline or acidhydrolysis.

Condensed tannin extracts, such as wattle and quebracho, are composed ofapproximately 70% polyphenolic tannins, 20% to 25% nontannins, mainlysimple sugars and polymeric carbohydrates (hydrocolloid gums), thelatter of which usually constitute 3% to 6% of the extract and heavilycontribute to extract viscosity, while the balance is accounted for by alow percentage of moisture. Although the exact structure is not known,it is believed that the main polyphenolic pattern in quebracho tanninsis represented by flavonoid analogues based on resorcinol A andpyrogallol B rings.

The word "tannin" as used herein and in the claims, unless otherwisespecified, refers to and includes the gallotannins and the flavotannins.Examples of the gallotannins include: tannic acid or Chinese tannin;Turkish tannin; Hamamelis tannin; Acer tannin; Glucogallin; Sumactannin; Valonia oak gall tannin; tea tannin; and tannins of Tara,Myrabolam, Divi-Divi, Algarobillo, oak, and chestnut. Examples offlavotannins include tannins from Gambier and catechu or Burma Cutch,quebracho, Tizerah, Urunday, wattle, mangrove, spruce, hemlock, larch,willow, pecan shells and Avaram. Said flavotannins are the presentlypreferred tannins for use in accordance with the invention.

Quebracho is the most preferred tannin. Quebracho is extracted from thebark and wood of the quebracho tree with water. The conventional methodof preparing quebracho is to disintegrate the wood and bark, extract thebark and/or wood with water, after which the solution of quebracho andwater is evaporated to about an 85 percent concentration of quebrachoand the concentrated quebracho is spray dried. Quebracho is the mostcommon commercial catechol tannin or flavotannin product. The hightannin content (about 20 percent) of the wood of the quebracho treemakes it the most important source of catechol tannins. The principalcommercial source of gallotannins is gall nuts. Preferred tanninmaterials will contain at least about 60% by weight of compoundsidentified as tannins.

The weight ratio of rosin to tannin in the blend may vary broadly.Preferred blends have ratios that are closer to equal proportions ofrosin and tannin, e.g. a weight ratio of from about 3:1 to about 1:3,more preferably from about 1.5:1 to about 1:1.5. Preferred compositionshave a weight ratio of rosin to tannin of greater than about 1:2, e.g.from about 2:1 to about 1:1.5.

Because the blend is composed of carboxylic acids and phenols, it will,if unneutralized, have a pH on the acid side, e.g. from about pH 3 toabout pH 5. To be active as an air entrainment agent, a substantialamount of the carboxylic acids in the rosin must be present in thecarboxylate form. While the cementitious compositions to which the blendwill be added are typically alkaline, it may not be strictly necessaryto neutralize the blend prior to its addition to a cementitiouscomposition. However, pre-activating the blend by pre-neutralizationwill facilitate efficient incorporation of active air entrainingmaterial into the cementitious composition. Thus, if the rosin asobtained is not pre-neutralized, the blend should further contain analkaline material in an amount sufficient to neutralize said blend, i.e.impart to an aqueous dispersion or solution of said blend an essentiallyneutral or alkaline pH, e.g. a pH of from about 6 to about 13. Examplesof useful alkaline materials include alkali or alkaline earthhydroxides, oxides or carbonates, e.g. sodium hydroxide, caustic soda(i.e. a blend of sodium hydroxide and sodium oxide), potassiumhydroxide, sodium carbonate, potassium carbonate, aqueous ammonia,calcium oxide, and calcium hydroxide.

The blend can be used either as a dry blend or as an aqueous dispersionor solution of the components. Efficient dispersion of the blend inwater at relatively low blend solids, e.g. 5% to 25% blend solids,facilitates dispersion of the blend throughout the cementitiouscomposition. Thus, the blend is preferably added to the cementitiouscomposition as an aqueous dispersion or solution which contains a majoramount by weight (i.e. at least 50% by weight) of water (preferablysoftened water or water containing a chelating agent for hardeningminerals, e.g. EDTA), and a minor amount by weight of the blend of rosinand tannin. As discussed above, the aqueous dispersion or solution ispreferably adjusted to a substantially neutral or alkaline pH with analkaline material.

The air entrainment agent may be added to a cementitious composition,e.g. a cement or a concrete mix, at any convenient point during itspreparation, after which point substantial mixing of air will takeplace. For example, the blend may be added to portland cement clinkerprior to grinding and thoroughly mixed with the cement during grinding.The blend may also be blended with the ground cement. The blend may beadded to the water in which the cement, sand and/or gravel are mixed.The cement may be premixed with water and then either a dry or aqueousblend composition may be added. In general, either a dry or aqueousblend composition may be added to the cement, mortar or concrete mix atany stage prior to final mixing with air.

Cementitious compositions are cements, mortars, or concrete mixes whichinclude concretes, mortars, neat paste compositions, oil well cementslurries, grouting compositions and the like. Cementitious compositionsare discussed in the encyclopedia article "Cement" cited below. Thecements used in the preparation of the cementitious compositions,especially concrete mixes, include Type I, II and III cements. Thesecements are well known and are described in "Cement", Encyclopedia ofChemical Technology, (Kirk-Othmer, eds, John Wiley & Sons, Inc., N.Y.,N.Y., 5th ed., 1993), vol. 5, pp. 564-598, the disclosure of which isincorporated by reference herein. Portland cement is by far the mostwidely used hydraulic cement. The term "hydraulic cement" as used hereinincludes those inorganic cements which, when mixed with water, set andharden as a result of chemical reactions between the water and thecompounds present in the cement. The term "Portland cements" as usedherein includes those products prepared by heating a mixture oflimestone and clay or shale, or other calcareous and argillaceousmaterials to a fused state and grinding the fused product, which iscalled clinker, with a few percent, normally about 4 to 6 percent, of aretarder such as gypsum. The term "concrete" as used herein includes amixture of such hydraulic cements and inert aggregates. Typicalaggregates include conventional aggregates such as gravel, sand,granite, limestone, and quartz sieve. Conventional hydraulic cementconcretes, e.g. Portland cement concretes, employ major amounts, i.e.over 50%, usually up to about 75% by volume of such aggregates in theset product. Pozzalonic materials such as condensed silica fume and flyash may also be included. The cements may be used to prepare concretemixes containing 100 parts by weight of cement, from about 140 to about260 parts by weight of sand, from about 100 to about 200 parts by weightof gravel, from about 35 to about 60 parts by weight of water and anamount of the blend composition of the invention effective to entrainthe desired amount of air into the cementitious composition upon mixingwith air. Preferred concrete mixes contain 100 parts by weight ofcement, from about 160 to about 240 parts by weight of sand, from about120 to about 180 parts by weight of gravel, from about 35 to about 60parts by weight of water and an amount of the blend of this inventioneffective to entrain the desired amount of air into said composition.

The concentration of blend composition of this invention in thecementitious composition may vary, but will generally be less than about1%, typically from about 0.0005% to about 0.5%, preferably from about0.001% to about 0.01% (by weight of cement). After preparation, thesecementitious compositions are then allowed to harden to obtain ahardened cement mass.

The amount of air to be entrained into the cement will depend upon thedegree of freeze damage resistance desired in relation to the sacrificeof strength that can be tolerated. In general, the amount of airentrained will be less than about 15% by volume of the foamedcementitious composition, generally from about 5% to about 10%. Theamount of air entrained into the cementitious composition can bedetermined in accordance with ASTM Method No. C-231, the disclosure ofwhich is incorporated herein by reference. The mixing techniquescommonly employed in mixing the solid and liquid components of thecementitious composition will typically also suffice to mix in thedesired amount of air, but techniques and/or mixers specificallydesigned to add air to the mix can be employed, if desired.

For a fuller understanding of the nature and advantages of thisinvention, reference may be made to the following examples. Theseexamples are given merely to illustrate the invention and are not to beconstrued in a limiting sense. While the invention has been describedwith reference to certain specific embodiments thereof, it is understoodthat it is not to be so limited since alterations and changes may bemade therein which are within the full intended scope of the appendedclaims. All quantities, proportions and percentages are by weight andall references to temperature are °C. unless otherwise indicated.

EXAMPLES Example 1

A solution or dispersion within the scope of this invention was preparedby mixing 7.5 parts by weight of a rosin gum (available as M grade fromAkzo Coatings, Inc., Baxley, Ga., and described as being comprisedmostly of abietic, levopimaric, isopimaric and palustric acids). 7.5parts by weight of quebracho tannin (available from Pilar River PlateCorporation, Newark, N.J. and described as containing 65% tannin, 10%non-tannin, 9.5% insolubles and 15.5% moisture), 5 parts by weight of a50% solids solution of caustic and 80 parts by weight of water. Themixture exhibited a pH of 12.2 and was a dark brown, opaque liquid thatappeared as a clear reddish solution upon dilution.

Example 2

A series of concretes were prepared by charging 5.45 kilograms ofPortland cement, 10.9 kilograms of sand, 8.17 kilograms of gravel, andan initial amount of water (the amount was recorded) to a cement mixerand mixing was begun. Additional water was added until the gravel beganto show wetness (the amount was recorded) and mixing was continued forabout 3 minutes. Mixing was then stopped and the concrete mixture wasallowed to sit in a quiescent state for 2.5 minutes.

Additives used in preparing the concrete mixes were as follows:

Additive A: a blend of the rosin and tannin of Example 1, but at thesolids shown in the following table.

Additive B: a rosin gum available from Akzo Coatings, Inc., Baxley, Ga.,under the designation of M grade and described as being comprised mostlyof abietic, levopimaric, isopimaric and palustric acids.

Additive C: a resin available from W. R. Grace & Co., Cambridge, Mass.,under the trade name "Daravair" and believed to be derived from southernpine stumpwood and comprised of a complex mixture ofhigh-molecular-weight phenolic compounds, resin acids, and neutralmaterials (and believed to be similar to Vinsol NVX resin, availablefrom Hercules Incorporated).

Additive D: a neutralized tannic acid material.

Additive E: industrial grade fatty acids available from HenkelCorporation, Ambler, Pa., as Aliphat 34R.

An aqueous sample of each additive was prepared at the solids shown inthe following table. Each aqueous sample in the amount shown in thefollowing table was then poured over a widespread area of the exposedsurface of the mixture within 30 seconds. (As can be seen from thefollowing table, the amount of each aqueous sample was adjusted inrelation to the solids content of the aqueous sample so that 0.0055% ofsolids additive based on the weight of the cement (5.45 kilograms) waspresent in the resulting concrete mix.) Mixing of the concrete mixturewas then resumed and additional water was added (the amount wasrecorded) if the mixture did not flow adequately. The concrete was thenmixed for an additional two minutes. The water:cement weight ratio (W:CRatio) of each sample is set forth in the following table along with thevolume % of air entrained, as determined by ASTM Method C-231,immediately after mixing was concluded (initial) and at 20 minutes aftermixing was concluded.

                  TABLE 1                                                         ______________________________________                                        EFFECT OF ADDITIVES ON AIR                                                    ENTRAINMENT IN CONCRETE                                                       Additive                     Air Entrained                                    Solids                       (Volume %)                                       Identity                                                                             (wt %)   Amount (g)                                                                              W:C Ratio                                                                              Initial                                                                             20 min.                              ______________________________________                                        (none) 0        6.0       0.508    2.92  2.81                                 A      5.0      6.0       0.508    7.50  6.57                                 A      5.0      12.0      0.508    10.95 10.55                                C      5.0      6.0       0.508    6.66  6.96                                 C      5.0      12.0      0.508    9.32  9.27                                 B      15.0     2.0       0.495    6.98  6.53                                 B      15.0     1.0       0.495    5.39  4.96                                 B      15.0     4.0       0.495    9.10  8.30                                 C      15.0     2.0       0.495    7.20  6.20                                 A      5.0      6.0       0.495    7.64  7.25                                 C      5.0      6.0       0.495    7.18  6.81                                 D      5.0      6.0       0.495    3.26  2.63                                 E      5.0      6.0       0.495    4.58  4.52                                 ______________________________________                                    

What is claimed is:
 1. A composition, useful for entraining air into acementitious composition, comprising a rosin and a tannin material in aratio by weight of from about 10:1 to about 1:10.
 2. A composition asclaimed in claim 1 wherein said composition is a dry powder.
 3. Acomposition as claimed in claim 1 wherein said composition has amoisture content of less than about 20% by weight.
 4. A composition asclaimed in claim 1 wherein said composition has a sufficiently lowmoisture content to render said composition flowable.
 5. A compositionas claimed in claim 1 which further contains an alkaline material in anamount sufficient to neutralize said blend.
 6. A composition as claimedin claim 1 which further contains at least 50% by weight of water.
 7. Acomposition as claimed in claim 6 wherein said composition is an aqueousdispersion or solution containing said blend at a solids content of fromabout 5% to about 50% by weight.
 8. A composition as claimed in claim 7wherein said solids content is from about 10% to about 15% by weight. 9.A composition as claimed in claim 6 which further contains an alkalinematerial in an amount sufficient to neutralize said blend to anessentially neutral or alkaline pH, of from about pH 6 to about pH 13.10. A composition as claimed in claim 1 wherein said rosin is comprisedof at least about 50% by weight of carboxylic acids.
 11. A compositionas claimed in claim 10 wherein said rosin is comprised of at least about50% by weight of monocarboxylic acids.
 12. A composition as claimed inclaim 1 wherein said rosin is an unmodified gum rosin.
 13. A compositionas claimed in claim 10 wherein said rosin is comprised of at least about50% by weight of monocarboxylic acids of alkylated hydroxyphenanthrenecompounds.
 14. A composition as claimed in claim 1 wherein said tanninmaterial is a natural tannin material.
 15. A composition as claimed inclaim 1 wherein said tannin material comprises a flavotannin.
 16. Acomposition as claimed in claim 1 wherein said tannin is quebrachotannin.
 17. A composition as claimed in claim 1 wherein said tanninmaterial is comprised of at least 60% by weight of compounds identifiedas tannins.
 18. A composition as claimed in claim 1 wherein said rosinis comprised of at least about 90% by weight of monocarboxylic acids.19. A composition as claimed in claim 1 wherein said weight ratio ofrosin to tannin material is from about 3:1 to about 1:3.
 20. Acomposition as claimed in claim 1 wherein said weight ratio of rosin totannin material is greater than 1:2.
 21. A composition as claimed inclaim 1 wherein said weight ratio of rosin to tannin material is fromabout 1.5:1 to about 1:1.5.
 22. An air entrainment agent useful forentraining air into a cementitious composition, the air entrainmentagent being comprised of a blend of an unmodified gum rosin comprised ofat least about 50% by weight of monocarboxylic acid compounds and atannin material comprised of at least 60% by weight of compoundsidentified as tannins in a ratio by weight of said rosin to said tanninmaterial of from about 2:1 to about 1:1.5, said blend yielding anaqueous solution or dispersion having a pH of from about pH 6 to aboutpH
 13. 23. A cementitious composition comprising a hydratable cement andfrom about 0.0005 to about 0.5% by weight of the cement of an airentrainment agent consisting essentially of a rosin and a tanninmaterial, the ratio by weight of said rosin to said tannin materialranging from about 10:1 to about 1:10.
 24. A composition as claimed inclaim 23 wherein the air entrainment agent is present at from about0.001% to about 0.1% by weight based on the weight of said cement.
 25. Acomposition of claim 23 wherein said cement is a Portland cement.
 26. Acomposition of claim 23 wherein said cementitious composition is aconcrete formulation comprising at least one cement selected from thegroup consisting of Portland cement type I, Portland cement type II, andPortland cement type III.
 27. A method of entraining air into acementitious composition comprising cement and water which comprises:mixing with the cementitious composition from about 0.0001% to about0.5% by weight of the cement of an air entrainment agent comprising arosin and a tannin material in a ratio by weight of from about 10:1 toabout 1:10.
 28. A method as claimed in claim 27 wherein the amount ofsaid air entrainment agent is effective to entrain from about 1% toabout 20% by volume of air into said cementitious composition.